ARTICLES
Combining Information From Multiple Sources in the Diagnosis of Autism Spectrum Disorders

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ABSTRACT

Background

Standard case criteria are proposed for combined use of the Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule to diagnose autism and to define the broader category of autism spectrum disorders.

Method

Single and combined Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule algorithms were compared to best estimate diagnoses in four samples: U.S. (n = 960) and Canadian (n =232) participants 3 years and older, U.S. participants younger than 36 months(n = 270), and U.S. participants older than 36 months with profound mental retardation (n =67).

Results

Sensitivities and specificities of 80% and higher were obtained when strict criteria for an autism diagnosis using both instruments were applied in the U.S. samples, and 75% or greater in the Canadian sample. Single-instrument criteria resulted in significant loss of specificity. Specificity was poor in the sample with profound mental retardation. Lower sensitivity and specificity were also obtained when proposed criteria for broader spectrum disorders were applied.

Conclusions

The Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule make independent, additive contributions to the judgment of clinicians that result in a more consistent and rigorous application of diagnostic criteria.

Section snippets

Participants

Data were collected from 1,039 participants who completed a diagnostic evaluation at the University of Chicago Developmental Disorders Clinic (N =627; 497 males, 130 females), the University of Michigan Autism and Communication Disorders Center (N = 150; 115 males, 35 females), as part of a longitudinal study conducted through TEACCH Centers at the University of North Carolina, Chapel Hill (N = 129; 100 males, 29 females) and the University of Chicago (N = 80; 69 males, 11 females), or in a

Autism Diagnosis Case Criteria

Preliminary correlations between the diagnostic instruments showed the ADI-R total scores correlated 0.57 with ADOS total scores. Table 2 shows the results from applying five criteria using the ADI-R, the ADOS, or a combination of both for establishing an autism diagnosis, ordered from the most stringent (requiring autism diagnoses from both instruments) to the least stringent (requiring an autism diagnosis from either instrument).

Participants

The Canadian sample of 232 mainly white participants was ascertained as part of a genetic study of ASD. Families with more than one child with ASD were recruited; singleton participants were randomly selected for comparison purposes. As shown in Table 1, 79% of the participants had autism (79%), 8% had ASD (PDD-NOS or Asperger disorder), and 13% had nonspectrum diagnoses, most commonly language disorder or learning disability.

Procedure

The ADI-R and ADOS were administered in variable order to all

RESULTS: STUDY 2

Because only 19 cases in this sample had BE diagnoses of nonautism ASDs, analyses were conducted for autism criteria only. As in study 1, the combination of ADI-R and ADOS autism classifications yielded the most balanced sensitivity and specificity. As shown in Table 2, the positive predictive value of the stringent criteria was high, but because of the small number of nonautism participants, the negative predictive value was much lower than for the U.S. sample. Relaxing the ADOS (AUT) criteria

DISCUSSION

Autism spectrum diagnostic case criteria that use combined information from the ADI-R and ADOS better reflect consensus clinical judgments of autism and ASD than any single instrument. We do not know whether these results are specific to the ADI-R and ADOS or are specific to the areas covered by the different methods. The ADI-R provides a developmental history, a detailed description of the individual'S functioning in a variety of social contexts, and the opportunity to take into account

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    This work was supported by grants NIMH R01 MH066496 and R01 MH46865 to Dr. Lord and was carried out as part of the NICHD/NIDCD Collaborative Programs for Excellence in Autism. The authors gratefully acknowledge the families who participated in these research projects and the staff at the TEACCH centers in North Carolina, the Department of Psychiatry at the University of Chicago, and the University of Michigan Autism and Communication Disorders Center.

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